Estimating topsoil water content of clay soils with data from time-lapse electrical conductivity surveys

Abstract

Spatial estimation of soil-water content (θ) at the field, hillslope, or catchment scale is required in numerous applications. Time-lapse electrical resistivity and apparent electrical conductivity (EC a) surveys are recognized as a useful source of information about both spatial variations in θ and spatial differences in soil properties. The objective of this work was to test the hypothesis that the accuracy of the regression relationships between θ and collocated EC a survey data can be improved for any given time if several time-lapse EC a surveys rather than a single EC a survey are used. Vertisol plots under conventional tillage and direct drilling were surveyed for gravimetric θ (θ g) in the top 0.3-m layer at 17 times and for topsoil EC a at 13 times in 2008 through 2010. Both dry and wet periods were covered by the surveys. On four occasions, θ g and EC a surveys were done on the same day. Only weak correlations (with R < 0.21) were found between EC a and θg measured on the same day. The accuracy of regression predictions of θ g substantially improved when data of several EC a surveys, rather than a single survey, were used. Therefore, the knowledge about the temporal variability in soil properties, as captured by the time-lapse EC a data, can improve the estimation of spatial variability in soil properties affecting soil-water content. Copyright © 2012 by Lippincott Williams & Wilkins.